Swim fins used by swimmers, body surfers, divers, and others in water are artificial fins, typically, of material like a resilient molded rubber or thermoplastic material, like ethylene-vinyl acetate (EVA), to improve propulsion speed and water agility. Swim fins may be prepared of synthetic materials, but one existing practice in the swim fin industry is to employ a swim fin having differential stiffness characteristics.
U.S. Pat. No. 5,290,194, issued Mar. 1, 1994, hereby incorporated by reference, discloses a swim fin which includes shoe and blade portions divided into longitudinal plural regions, each region representing an area of the fin formed from a particular material and of predetermined durometer range, so that the instep and toe region have different stiffness properties.
European Patent No. 0 436 927, published Jul. 17, 1991, as well as an improvement U.S. Pat. No. 5,435,764, issued Jul. 25, 1995, discloses a swim fin with a composite, partially multilayered blade section with a separate soft shoe section and an attached blade section composed of a base layer of a fairly rigid thermoplastic material, like ethylene-vinyl acetate (EVA) and a partial or full outer or top layer of a more resilient material, like a soft thermoplastic rubber.
It is desirable to provide a new and improved multilayered swim fin of controlled and selected durometer hardness and method of manufacture of such swim fins.